HDR 16bit limit

[Eikon]

hey all. so, wasnt sure on the title, heres the problem....

iv used hdri's for a long time at work doing 3d effects for movies. we drop em in to the background to help cast realistic light on the models we are rendering. id never realy given much thought to them other than 'is this hdr usable for my purposes today'. sometimes we were provided with them, sometimes id go download my own.

anyway, now that im getting into photo processing, maniplution, etc as a hobby, im getting into shooting my own hdrs. not so much to achieve that oh-so-cliche hdr toned look, but more for flexibility in backgrounds and processing later.

im including some samples here of a 12 exposure hdr i shot the other day. my problem is that photoshop is .... lets say less functional... working in 32 bit mode as most of the filters and adjustments are not available. this limits me to working in 16bit mode (note iv not actually tried to work in 32bit mode yet... maybe it would be ok?), which thereby limits the hdr to being a 16bit image, not a 32bit image and completely defeats the purpose of having high dynamic range.

so here are my images to illustrate my problem...

merged hdr at normal exposure
http://i56.photobucket.com/albums/g1...h/hdrmerge.jpg

max exposure possible
http://i56.photobucket.com/albums/g1...axExposure.jpg

min exposure possible
http://i56.photobucket.com/albums/g1...inExposure.jpg

so the problem is, in 16bit mode, this is what happens when you start tryin to adjust the exposure...

16bit exposure adjustment
http://i56.photobucket.com/albums/g1.../expAdjust.jpg

16bit gamma adjustment
http://i56.photobucket.com/albums/g1...h/expGamma.jpg

the gamma adjustment is closer, but still not correct. so, whats the solution here? just suck it up and work in 32bit mode? or am i missing some little trick about hdr's?


oh and just cause the results were nice, the photomatix exposure fusion version...

http://i56.photobucket.com/albums/g1...idExposure.jpg


input appreciated. thanks all!

[mcdronkz]

You could apply some manual tone mapping, contrast, gamma and exposure adjustments to the image in 32 bit mode. You can then convert it back to 16 bit mode using the 'Exposure and Gamma' method or just use it as a 32 bit Smart Object within a 16 bit file as a foundation for further adjustments.

[Eikon]

hmmm... the smart object idea is interesting. ill hafta play with that. the idea was to be able to put an exposure adjustment ontop of it, and then via a mask, control the exposure by painting. that wouldnt work in 16bit mode. probably wouldnt work as a smart object either, but if i could edit the smart object that might work.... bit of a pain of a work flow though. ill try that.

[mistermonday]

Eikon, your 12 exposures have very adequately captured the entire dynamic range of the scene. What you should be doing is merging the source images (preferably RAW) in a dedicated HDR application like Photomatix or PhotoEngine, and then tone map the resulting 32 bit file. Once tonemapped, there is no point trying to further process it in 32 bit. The tonemapped result should be saved as 32 bit TIFF and then fine tuned in PS if required.
Regards, Murray

[Eikon]

My tone map test was in photomatix and i dont think it has a 32bit save option. When doing the hdr in cs5, the only 32b processing option is the exposure/gamma slider option which does no tone mapping. There is a tone mapping adjustment in cs5 though, right? If that did the same thing as photomatix, well problem solved i guess. Ill try that in the morning.

[mistermonday]

Originally Posted by Eikon

My tone map test was in photomatix and i dont think it has a 32bit save option. When doing the hdr in cs5, the only 32b processing option is the exposure/gamma slider option which does no tone mapping. There is a tone mapping adjustment in cs5 though, right? If that did the same thing as photomatix, well problem solved i guess. Ill try that in the morning.

Photomatix will allow you to save the intermediary 32 bit file. Check that box in the "Load Bracketed Photos" dialog box. After the images are merged you can save the 32 bit file as a .hdr radiance file. However, you seem to be hung up on working in 32 bit, why? A 32 bit file linear file can not be represented properly on any monitor or output device. You need to tone map it into the visual field which is 8 and 16.
Also, fwiw, of all of the HDR s/w out there, PSCS5 is generally considered about the worst for HDR processing.

[Chain]

If I understand this correctly then I believe Eikon will not be using the HDR image "as-is" on screen or print, but rather as a texture/light/environment when doing 3D/compositing. For this purpose the files should remain in 32-bit, and I believe you can do the basic tweaks you need in camera raw (white balance etc. before merging) and Photoshop.

Tone mapping (and converting to 8 or 16-bit) is useful if you want to try and show the full dynamic range in a single "exposure", but you loose the HDR info that can be so useful in 3D scenes.

Depends on the use... What is it you feel you need to do to the HDR image in Photoshop? Color adjustment? Cloning/healing? I believe that should work (but haven't tried it).

[Eikon]

actualy Chain, no its not for lighting, its for a background in a photo. its not realy that i currently want to achieve anything specific in PS. i just used photomatix to make my test hdr, saved it as a 16b tiff, brought it into PS, and was pissed off that i lost all that dynamic range. i dont need or want to work in 32bit mode to have access to all that data... but maybe thats the only way around it.

ill try the checkbox 32b thing in photomatix and save out the radiance file, then cobble together some workflow so i can use it in PS. all i realy wanted was access to the complete luminance range so i can darken and brighen to taste, selectively.

... and good to know about the PS hdr merge being a big pile

[mcdronkz]

Originally Posted by Eikon

i dont need or want to work in 32bit mode to have access to all that data... but maybe thats the only way around it.

You should read the HDRI handbook by Christian Bloch, it will be a great help in working with HDR files.

[Eikon]

i SHOULD do alota things, haha. right now im still poking around, jumping back and forth between PM and PS. but thanks for the tip on the book.

[Chain]

Ah, I thought you would use the image for something more than just a background image. 16 or 8 bit will do then (unless you will be varying the exposure throughout an animation).

I've not tried much HDR myself, just tested it briefly in Photoshop just to see how it worked. Not happy with the result of the tonemapping I did so I just stopped there. I don't take much photos any more, so I don't really encounter it.